I gave mine FOC Sideswipe's ridiculous gun. Those little red accents on it help tie it to Optimus. I did want him to hold it by the main peg so it would have that sticky-up block at the rear end to better evoke G1 Op's rifle, but the flap behind the hand and a piece sticking out the back of the gun 'turbine' assembly prevented that. So he's holding it by the side peg on the gun instead. Still works though.
I totally stole the gun off my BH Voy Optimus who had been keeping it warm for Sideswipe. I think that gun is destined to be passed around each Optimus toy that gets released while Sideswipe will just have to make do with whatever's left spare. Right now he's got one of those little blind-bagged TFP Optimus figures that turns into a gun.
Hmmm... I have WFC Cliffjumper using that gun but now I might need to give Optimus that one and give Cliff one of the Wrecker's guns. EDIT: It is actually is possible to hold the gun the way you originally wanted. rotate optimus' hand so that the bottom of the fist is against the plate. Then carefully insert the gun SIDEWAYS then rotate it into the correct position. This lets Optimus hold it correctly.
Optimus is an even happier camper now. I don't normally swap weapons around (it drives my OCD nuts) but Sideswipe's gun was just too ridiculously big for him to use. Not entirely sure what they were thinking giving him that. Never did work out what that round notched gap in the end is for either.
+1 Thanks I totally forgot I had this! Some guy threw the black version in with a purchase I made and the only guy I had who could hold it was ugly G2 Pastellimus Nerf Prime. Only thing he's good for was to hold onto that for me Looks much better now with Evasion. OK maybe a little on the big side.
Can he hold the Dr. Wu Rain Storm Gun or will the ammo magazine bump into the panel jutting out under his hand? Does he look any good dual-wielding those?
Its so you can put the gun over the spoiler like an anti-air gun or something, like this. http://www.16bit.com/fotd/fotd-pics/0575-gen-transformers-2012-Sideswipe3.jpg